Refactor Mihomo traffic and memory handling to use streaming GET requests

- Updated `GATEWAY_RUN.md` to clarify the use of streaming HTTP GET for traffic and memory metrics instead of WebSocket connections, addressing potential issues with WebSocket stability behind nginx.
- Modified the Svelte component to implement streaming GET requests for `/traffic` and `/memory`, improving data retrieval and reducing connection issues.
- Enhanced the `recordRates` function to handle totals from the streaming response, ensuring accurate metric tracking.

web/src/lib/api/client.ts

@@ -20,7 +20,10 @@ export function mihomoUrl(alias: string, path: string): string {
 	return `${gatewayBase()}/api/${encodeURIComponent(alias)}/mihomo/${p}`;
 }
 
-/** WebSocket к тому же origin (ws / wss). */
+/**
+ * WebSocket к тому же origin (ws / wss).
+ * Для /traffic и /memory во фронте предпочтительнее потоковый GET через `mihomoUrl` — тот же прокси, что и для REST; WS из браузера часто рвётся за nginx.
+ */
 export function mihomoWsUrl(alias: string, path: string): string {
 	const p = path.replace(/^\/+/, '');
 	const base = gatewayBase();